1. Technical Field of the Invention
The present invention relates generally to pressure sensors. More particularly, the invention relates to an improved pressure sensor that has a compact size and high corrosion resistance and ensures high accuracy in sensing a pressure.
2. Description of the Related Art
Conventionally, wire bonding has been used to make an electrical connection for a pressure sensor.
For example, as shown in FIG. 8, a pressure sensor 200 includes a sensor chip 102, an integrated circuit chip 103, and a substrate 100.
The sensor chip 102 is configured to sense a pressure of a fluid and generate an electrical signal representative of the sensed pressure. The sensor chip 102 is joined to the upper surface of a glass seat 101, and disposed on the substrate 100 together with the glass seat 101.
The circuit chip 103 includes a circuit that is configured to process (e.g., amplify) the electrical signal generated by the circuit chip 102, and also disposed on the substrate 100.
In the above pressure sensor 200, wire bonding is used to make an electrical connection between the different members of the pressure sensor. Specifically, the sensor chip 102 has a plurality of electrical contact pads 102a that are made of aluminum and electrically connected to the substrate 100 by wire bonding 104; the circuit chip 103 has a plurality of electrical contact pads 103a that are also made of aluminum and electrically connected to the substrate 100 by wire bonding 105. As a result, the sensor chip 102 and the circuit chip 103 are electrically connected with each other.
However, in the above arrangement, the electrical contact pads 102a and 103a of the sensor chip 102 and the circuit chip 103 are to be exposed to an environment around the pressure sensor 200. When the environment is a corrosive one, for example, an acidic atmosphere, those electrical contact pads will be corroded accordingly, thereby resulting in an electrical connection failure.
As an alternative, Japanese Patent No. 3,198,779, an English equivalent of which is U.S. Pat. No. 5,595,939, discloses a pressure sensor that is configured to sense a pressure of a highly corrosive fluid.
According to the disclosure, the pressure sensor has a structure in which a sensing element is connected to connector pins by wire bonding, and all the sensing element, bonding wires, and connector pins are placed in oil and sealed by means of a corrosive resistant metal diaphragm.
However, with such a structure, the pressure sensor necessarily includes the metal diaphragm, the oil, an O-ring for sealing, etc., thus resulting in great difficulty in making the pressure sensor compact.